The invention relates to improvements in vehicle brake boosters. This application is being filed concurrently with Ser. No. 189,872, now U.S. Pat. No. 4,850,262, for related subject matter, further identified by R. 21203. Brake boosters are typically incorporated between the brake pedal to be actuated and the master brake cylinder; after actuation of the brake pedal, brake boosters generate a brake pressure independently of the pedal braking force exerted. To this end, after brief actuation of the brake pedal, a connection of a work chamber to a reservoir or supply container is opened, and brake fluid is fed out of the reservoir or the supply container into the work chamber, for example via a pump. The expanding work chamber actuates a servo piston under pressure, and this piston transfers the pressure to the master brake cylinder, thereby boosting the brake pressure.
Once the brake pressure is reduced again, a return flow line for the brake fluid located in the work chamber must be provided, so that the servo piston can be relieved as well. This interplay between the opening and closing of the inflow of brake fluid to the work chamber and the control of its return flow plays a considerable role in the braking operation. Because of the many seals that are used to prevent leakage due to the brake fluid movement, the danger of leakage is very great. Also, pressure jumps, which feel unpleasant to the driver, frequently occur when the inflow and return lines close.